Potential-transformer.



0. W. LUNNON & E. HARVEY.

POTENTIAL TRANSFORMER.

APPLICATION FILED 1An.27.1913.

Patented Sept. 28, 1915.

.strips of the main core,

' will correspond to the Outline 'OTTO w. LUNNON AND EARL HARVEY, orDENVER, COLORADO.

POTENTIAL-TRANSFORMER.

To all whom it may concern:

Be itknown that we, OTTO W. LUNNON and EARL HARVEY, citizens of theUnited States of America, residing in the city and county of Denver andState of Colorado, have invented new and useful Potential- Transformers,of which the following is a specification.

This invention relates to electric current transformers.

The'object of the invention, is to provide a transformer having alaminated core comprising groups of metal strips, the strips of eachgroup being bent outward and around the adjacent portions of the primaryand secondary coils. Further, to provide a transformer having a mainlaminated core, and supplemental laminated core portions, which latterare disposed in opposite groups between the primary and secondary coils,the strips of one of said groups, and half of the being bent outwardlyaround the coils, their ends overlapping in alternate order, while thestrips of the other group and the other half of the strips of the maincore are oppositely bent around the coils, their ends overlapping in thesame manner. Further, to provide a transformer provided with a laminatedcore which is so wound or bent that its contour or circles described bythe lines of magnetic force, produced by the primary coil, and one inwhich joints are reduced toa minimum, thereby lessening the magneticreluctance. I attain these objects by the mechanism illustrated in theaccompanying drawings, in which:

Figure 1, is a longitudinal sectional View through the transformer as itappears before bending the strips of the laminated core around thewindings. Fig. 2 is a similar sectional view of the completedtransformer, the manner of bending the core forming strips or laminae,being clearly shown. Fig. 3 is a transverse sectional view thereof. AndFig. 4: is a view showing the manner of housing the transformer, thesame being shown in connection with a lamp circuit and bell.

Similar letters of reference refer to similar parts throughout theseveral views.

Referring to the accompanying drawings: The numeral 1 indicates alaminated core, composed of thin iron strips of suitable width, andsuflicient in number to produce Specification of Letters Patent.

Application filed J'anitary 27, 1913.

, their ends are in step fashion,

'tervals in the winding,

Patented Sept. 28, 1915.

Serial No. 744,551.

the required magnetic field. Half of these stripsare adapted to be bentaround in one dlrection so that their ends overlap, and half in theopposite direction, with their ends overlapp1ng; and'in order that theirends may overlap in such a manner as to prevent bunching and give thedesired outline to the transformer, I arrange them as follows: Thestrips are first cut in pairs-which vary in length, in regular order orstep form. Onehalf of the strips are then arranged so thatat one end ofthe group their ends are all flush, while at the other end of the groupor are shortened by regular intervals. The other half of the strips arearranged in the same manner and the two groups are then placed togetherwith their longest strips back to back, but so that the longest strip ofeach group extends a suitable distance beyond the Hush ends of the othergroup, the outside strip of each group being the shortest strip of thegroup, as will be fully understood by reference to Fig. 1. On oppositesides of the core thus formed are placed one or more short metal strips2, which not only become part of the core, but are primarily intended todefine the bending points of the two groups of core strips, and preventthem from crowding the ends of the primary coil, s the said strips arebent around. Around hese strips and the other strips composing the core,is wound one or more layers of any suitable flexible insulating material3, such as what is known as Empire cloth, the strips having first beentightly wrapped with suitable tape to hold them firmly together. Aroundthis insulating wrapping is wound the fine insulated wire which formsthe primary coil or winding 4. This winding may consist of a greater orless number of turns to meet the requirements in the case, and at inthinstrips of insulating paper are wrapped about the wire, as shown at 5, toprevent the under or inner layers of wire from being crowded out ofposition by the surrounding layers, as will be understood.

Around the primary winding is wound one or more layers of insulatingmaterial 6,

of the kind above mentioned, the terminals 7 of the winding beingexposed for purposes of strips 8, of less length than the shorteststrips of the main group. These strips form additional core members, andupon them are placed one or more layers 9, of insulating material. Thesecondary coil 10, is then wound around these strips and the primarycoil, and upon opposite sides of the secondary coil, in line with theinsulating strips or layers, are placed layers 11 of insulatingmaterial. The strips of each group are then bent outwardly and aroundthe adjacent portions of the secondary coil, over the insulation 11, thestrips in each group being bent around in alternate order so that theirends overlap and rest one upon the other, as shown by Fig. 2, afterwhich the two groups of strips forming the main core are bent outwardlyand around the bent ends of the strips 8, those of each group being bentin alternate order, so that their ends overlap and rest one upon theother, in the same manner as the ends of the strips 8. After the stripsare thus bent, they are pressed firmly together, so as to give compactform to the transformer, and at the same time cause the strips to engageeach other at all points, thus preventing humming, which would otherwiseoccur, the current is on.

A suitable band, such as a cord or metal band, is then secured upon thecore to hold the strips in position. A metal band 12 is shown, for thispurpose. By surrounding the secondary coil with the core strips 8, acounter magnetic field is established, sufficient to keep thetransformer from overheating on overload. The terminals 18 of thesecondary coil, are extended as shown, for connection with feed wires.

In Fig. 4:, the transformer is housed in a metal box 14, having holes 15in its opposite ends, through which the ends of circuit wires areinserted for connection with the terminals of the transformer. This boxis of a' style in common use, and in practice is provided with a cover,which is omitted in the present instance. The width of the boxrelatively to the length of the transformer,

is such that when the transformer is placed therein, the ends of itscore engage the sides of the box, which thus produce a co-actingmagnetic field with the core. A bowed. metal plate 16, is placed overthe transformer, with its ends bearing against the ends and adjacentbottom portions of the box, and this plate is secured by means of theusual cement employed in such cases, and the plate is provided withapertures through which the terminals of the transformer coils extend.In Fig. 4, the transformer is shown in connection with a lamp and bellcircuit 17 and 18 respectively, and while it may be used in variousconnections, the particular style of transformer described above, and

illustrated in the accompanylng drawings, is

when

well adapted for use in connection with tungsten lamps, bells,mechanical toys, and in other cases where a low voltage is re quired.While the laminations of the core are shown as groups bent in oppositedirections, it is obvious that they could all be bent in the samedirection, and in this case the strips or laminations would be cut insuitable lengths, to meet the requirement of bending. I

Having described our invention, what we claim as new and desire tosecure by Letters- Patent, is:

1. A transformer as specified, consisting of a laminated core comprisingtwo groups of contacting metal strips, a primary coil surrounding thecore, a secondary coil surrounding the primary coil, the portions ofsaid groups of strips without the coils being bent in oppositedirections around the adjacent portions of the coils, the ends of thestripsof each group overlapping one another in alternate order, andsupplemental core strips between the primary and secondary coils incontact with the strips of the main core.

2. A transformer comprising a main laminated core, primary and secondarycoils surrounding said core one within the other, oppositely positionedsupplemental core strips interposed between the primary and secondarycoils, said main and supplemental core strips being bent around thecoils with their ends overlapping in alternate order.

3. In a transformer as specified, the combination with primary andsecondary coils, one surrounding the other, of a main laminated coreextending through the inner coil, and opposite supplemental laminatedcores interposed between the primary and secondary windings, saidsupplemental cores being bent in opposite directions around the coils,the ends of their strips overlapping in alternate order, one half of thestrips composing the main core being bent around over the adjacentsupplemental strips, while the remaining strips are bent around those ofthe opposite supplemental strips, the ends of each half of the stripsoverlapping in alternate order.

4. A transformer comprising a primary and secondary coil, one around theother, a laminated core extending through the inner coil, the halves ofits strips being bent in opposite directions around the coils, andsupplemental cores interposed between the primary and secondary coils,and in contact with the main cores, for producing a counter magneticfield.

5. In a transformer as specified, a laminated core, primary andsecondary coils surrounding the core one over the other, flexiblenon-conducting material between the core and inner coil, between theprimary and secondary coils, and upon the secondary coil,

oppositely arranged supplemental cores ex- In testimony whereof we affixour signatending betwefen the primary and secondary tures in presence oftwo Witnesses.

coils, the hal of the main core strips and 7 7 T Y the adjacentsupplemental strips being bent 5 in opposite directions from each otherto surround the adjacent portions of the coils, Witnesses: and a bandfor holding said strips in their G. SARGENT Enmo'rr, bendedpositions.ADELLA M. FOWLE.

